For centuries, various natural and unnatural compositions and/or compounds have been added to comestible (edible) foods, beverages, and/or orally administered medicinal compositions to improve their taste. Although it has long been known that there are only a few basic types of “tastes,” the biological and biochemical basis of taste perception was poorly understood, and most taste improving or taste modifying agents have been discovered largely by simple trial and error processes.
There has been significant recent progress in identifying useful natural flavoring agents, such as for example sweeteners such as sucrose, fructose, glucose, erythritol, isomalt, lactitol, mannitol, sorbitol, xylitol, certain known natural terpenoids, flavonoids, or protein sweeteners. See for example a recent article entitled “Noncariogenic Intense Natural Sweeteners” by Kinghorn et al. (Med Res Rev 18 (5) 347-360, 1998), which discussed recently discovered natural materials that are much more intensely sweet than common natural sweeteners such as sucrose, fructose, and the like. Similarly, there has been recent progress in identifying and commercializing new artificial sweeteners, such as aspartame, saccharin, acesulfame-K, cyclamate, sucralose, and alitame, etc., see a recent article by Ager, et al. (Angew Chem. Int. Ed. 1998, 37, 1802-1817). The entire disclosure of the two references identified above are hereby incorporated herein by reference, for the purpose of describing at least in part the knowledge of those of ordinary skill in the art regarding known sweetening agents.
However, there remains in the art a need for new and improved flavoring agents. For example, one of the five known basic tastes is the “savory” or “umami” flavor of monosodium glutamate (“MSG”). MSG is known to produce adverse reactions in some people, but very little progress has been made in identifying artificial substitutes for MSG. It is known that a few naturally occurring materials can increase or enhance the effectiveness of MSG as a savory flavoring agent, so that less MSG would be needed for a given flavoring application. For example the naturally occurring nucleotide compounds inosine monophosphate (IMP) or guanosine monophosphate (GMP) are known to have a multiplier effect on the savory taste of MSG, but IMP and GMP are very difficult and expensive to isolate and purify from natural sources, or synthesize, and hence have only limited practical application to most commercial needs in food or medicinal compositions. Less expensive compounds that would provide the flavor of MSG itself, or enhance the effectiveness of any MSG that is present could be of very high value. Similarly, discovery of compounds that are either new “High Intensity” sweetners (i.e. they are many times sweeter than sucrose) would be of value, or any compounds that significantly increase the sweetness of known natural or artificial sweeteners, so that less of those caloric or non-caloric sweeteners would be required, would be of very high utility and value.
In recent years substantial progress has been made in biotechnology in general, and in better understanding the underlying biological and biochemical phenomena of taste perception. For example, taste receptor proteins have been recently identified in mammals which are involved in taste perception. Particularly, two different families of G protein coupled receptors believed to be involved in taste perception, T2R5 and T1R5, have been identified. (See, e.g., Nelson, et al., Cell (2001) 106(3):381-390; Adler, et al., Cell (2000) 100(6):693-702; Chandrashekar, et al., Cell (2000) 100:703-711; Matsunami, et al., Number (2000) 404:601-604; Li, et al., Proc. Natl. Acad. Sci. USA (2002) 99:4962-4966; Montmayeur, et al., Nature Neuroscience (2001) 4(S):492-498: U.S. Pat. No. 6,462,148; and PCT publications WO 02/06254, WO 00/63166 art, WO 02/064631, and WO 03/001876, and U.S. Patent publication US 2003-0232407 A1). The entire disclosures of the articles, patent applications, and issued patents cited immediately above are hereby incorporated herein by reference, for all purposes, including their disclosures of the identities and structures of T2R5 and T1R5 mammalian taste receptor proteins and methods for artificially expressing those receptors in cell lines and using the resulting cell lines for screening compounds as potential “savory” or “sweet” flavoring agents.
Whereas the T2R family includes a family of over 25 genes that are involved in bitter taste perception, the T1R5 only includes three members, T1R1, T1R2 and T1R3. (see Li, et al., Proc. Natl. Acad. Sci. USA (2002) 99:4962-4966.) Recently it was disclosed in WO 02/064631 and/or WO 03/001876 that certain T1R members, when co-expressed in suitable mammalian cell lines, assemble to form functional taste receptors. Particularly it was found that co-expression of T1R1 and T1R3 in a suitable host cell results in a functional T1R1/T1R3 savory (“umami”) taste receptor that responds to savory taste stimuli, including monosodium glutamate. Similarly, it was found that co-expression of T1R2 and T1R3 in a suitable host cell results in a functional T1R2/T1R3 “sweet” taste receptor that responds to different taste stimuli including naturally occurring and artificial sweeteners. (See Li, et al. (Id.). The references cited above also disclosed assays and/or high throughput screens that measure T1R1/T1R3 or T1R2/T1R3 receptor activity by fluorometric imaging in the presence of the target compounds. We employed the above-described assays and/or high throughput screening methods to identify initial “lead” compounds that modulate the activity of T1R1/T1R3 “savory” taste receptors, or T1R2/T1R3 “sweet” taste receptors, then embarked on a long, complex and iterative process of investigation, evaluation, and optimization, so as to arrive at the various inventions described below.